Members such as members for use in a plasma chamber of semiconductor device production equipment are exposed to corrosive gas. Ceramics which are excellent in corrosion resistance are used for the members, because materials poor in corrosion resistance shorten the operation life of the equipment. Also, attachment of particles that are produced by the reaction of the members with the corrosive gas to the device can degrade the quality of the device. For such applications, materials (for example, AlN and Y2O3) more excellent in corrosion resistance than common ceramic materials as well as common ceramic materials (for example, alumina) are employed.
However, particles cannot be prevented completely only by altering the materials. There inevitably occur recessed portions (for example, pores, microcracks and machining scratches) on the surface layer of the ceramic members, because they are processed products of brittle materials. Fine particles generated during a surface grinding process or the like can enter into these recessed portions. It is difficult to completely remove the deposited fine particles in the recessed portions by an ordinary cleaning process. Microcracks may also occur during the production step of the ceramic members. The deposited fine particles or the microcracks are scattered as particles when they are exposed to a high temperature atmosphere, a treatment gas atmosphere, a plasma atmosphere or a vacuum atmosphere at the time of heat treatment.
Several methods for preventing the scattering of the particles derived from ceramic members have hitherto been proposed.
Patent Document 1 discloses an invention of “a method for cleaning a ceramic product, wherein the face to be cleaned of the ceramic product is coated with a solvent, then a film made of a material soluble in the solvent is brought into contact with the face, and the film is peeled off from the face and thus the face is cleaned.” According to this invention, the film portion in contact with the face to be cleaned is dissolved by the solvent, and follows the asperities of the form of the face and hence the particles present on the face are surrounded by the dissolved portion of the film. Consequently, when the film is peeled off from the face to be cleaned, the particles are fixed on the film side in contact with the face and thus the particles are removed from the face.
Patent Document 2 discloses an invention of “an alumina ceramic sintered body, wherein the alumina ceramic sintered body is composed of 99.2% by weight or more and 99.99% by weight or less of aluminum oxide and the balance consisting of the oxides of metals other than aluminum, and the average particle size of the alumina sintered body is 0.5 μm or more and 15 μm or less and the density of the alumina sintered body is 3.88 g/cm3 or more and 3.97 g/cm3 or less; and the sintered body or the sintered body subjected to grinding processing is heat treated at a temperature of 1000° C. or higher and 1550° C. or lower for 0.1 hour or more and 6 hours or less.”
Also proposed is a method for forming a coating film which has a high corrosion resistance, mainly with respect to thermal spraying ceramics, as a method for improving the corrosion resistance of a ceramic material.
Patent Document 3 discloses an invention of “a corrosion resistant composite member used in an environment of a halogen-based corrosive gas or in an environment of a plasma of a halogen-based corrosive gas, wherein the corrosion resistant composite member has a substrate and a coating film formed of a ceramic sol/gel, disposed on the substrate portion exposed at least to the halogen-based corrosive gas or a plasma of the halogen-based corrosive gas.”
Patent Document 4 discloses an invention of “a method for forming a composite coating film which has a corrosion resistance and being durable for a long term use, wherein a single metal, an alloy, a cermet or a ceramic is thermal sprayed to the surface of a substrate, preprocessed for spraying; then a pore-sealing solution satisfactory in permeability, forming a pore-sealer in the pores in the thermal sprayed coating film, is applied or impregnated to the substrate surface; pore-sealing treatment is performed by aging or heat treatment; a solution in which a glassy substance forming component is dissolved or suspended is applied to the treated substrate with a brush or spraying; the treated substrate is dried at normal temperature or fired at a temperature of 900° C. or lower; and thus a glassy surface layer coating film is formed.”
Patent Document 5 discloses an invention of “a composite coating material disposed on a ceramic member, wherein the composite coating material includes a ceramic porous body having open pores and a resin impregnated in the open pores”; in Examples of Patent Document 5, only a ceramic porous body formed by a thermal spraying method is described.
Patent Document 6 describes an invention of “a pore-sealed ceramic insulating layer, wherein in the ceramic insulating layer obtained by thermal spraying, by taking advantage of the contraction percentage difference due to the temperature difference, between a gas and a resin, pore-sealing bodies composed of a thermosetting resin are formed in the entrances of the pores generated in the ceramic insulating layer.”